1. Field-of-the-Invention
This invention relates to light controlling composite structures for enhancing the image quality of LCD displays, projection systems, and the like. The composite structures include micro lens arrays and carrier layers having optical properties.
2. Description of Related Art
The display of images, no matter whether static or dynamic, is of great importance to our everyday life. Portable electronic equipment and other electronic equipment having low power consumption display devices are now becoming a basic necessity.
Liquid Crystal Display (LCD) are one of the major technologies used in these display devices. The LCD is a passive device that cannot emit light. External lighting is necessary to use a LCD device. For many applications of the LCD device, batteries are used as the application""s only power source.
As a result, a better LCD system design needs to consider how to increase the light utilization efficiency. As indicated in FIGS. 24 and 25, a variety of optical materials and structures are typically used in order to improve the overall optical performance of an LCD display device. Nevertheless, there is a clear need for additional structures and materials that can enhance the light utilization efficiency of many of the LCD applications.
Another technology that has made great progress in recent years is the image projector. There are a variety of projector types depending on the device that is used to form the image. Some of the most recent developments include DMD (Digital Mirror Device, from Texas Instruments) projectors and LCD projectors. However, the final images from these projectors have to be displayed to the viewer via some kind of media. The display media usually have a large influence on the quality of the image a viewer sees, as do the final media that xe2x80x9cprocess or touchxe2x80x9d the image. Usually, a screen is used in such a setting. Depending on the viewer""s environment and the projection principle used, the screen can either be a xe2x80x9cfront projectionxe2x80x9d or xe2x80x9crear projectionxe2x80x9d type. FIG. 26 indicates one of the prior art designs that provides a rear projection screen using a sheet of polymer material that forms a plurality of lenses to modify the light path. FIG. 27 is a typical rear projection screen of the prior art, wherein a single layer of optical beads is used to enhance the optical performance of the rear projection screen. FIG. 28 is yet another prior art design that uses a polymer material similar to that of FIG. 26 while providing a different lens structure for optical path modification.
The requirements for projection display devices used for each application are different. For home entertainment, the user""s position in front of the display is likely to vary more in a horizontal than a vertical direction. For display devices used in a more public area, like a control room, an even wider horizontal spread is commonly encountered.
In general, it is desirable that a projection screen be capable of high resolution, high contrast, large gain and large viewing angle. But it is difficult to meet all these requirements simultaneously. For instance, the screen gain is often compromised when a larger viewing angle is requested. Tradeoffs are usually made in screen performance for each different application.
There is a need for improving the overall performance while meeting the minimum performance criteria necessary for the projection display application in which the screen is used, and in general to improve the image quality for these applications.
By way of background, conventional LCD and projector structures are shown in U.S. Pat. Nos. 4,666,248; 5,040,883; 5,467,417; 5,563,738; 5,917,664; and 6,317,263.
This invention relates generally to micro lens systems and articles thereof, and more generally, to micro lens systems and articles that may be applied to display devices suitable for use in LCD display systems and/or projection systems.
One article embodying the present invention includes carrier media layers having attached arrays of micro lens systems for modification of the light path, either horizontally and/or vertically.
The micro lens systems may have light dispersing surfaces and/or may contain an isotropic light disperser, such as light diffusing particles or other types of bulk diffuser. In either case, dispersion may be such that the direction of maximum light intensity is parallel to or at an angle relative to an axis normal to the carrier media""s major surface.
The carrier media layers of the composite structure may include combinations of reflective material, highly transparent material, light absorbing material, opaque material, photosensitive film, light dispersing material, metallic material, prism-like optical material, retarding material, polarizing material and/or any other functional material to provide extra modification of optical performance. In addition, the carrier media layers may each take the form of a film, plate, sheet, or any other suitable structure with an appropriate thickness, and may be formed with transparent apertures arrays or an opaque plastic or metallic material having grids of perforations, such that light pass through the apertures in the carrier media layers with no modification. Finally, the carrier media layers may be attached to each other or other supporting materials so as to provide a more rigid structure strength.
A number of micro machining technologies are now widely used to form miniature electrical, mechanical and optical devices and composite systems of these devices. Many new devices, such as micro motors and micro gears made by these micro machining technologies are now a well defined practice. One of the best known applications of this technology is the digital micro mirror device from Texas Instruments. This device now plays a key role in improvements to image projectors.
Miniature optical elements such as micro lenses can also be made, by the use of different technical tools, with good precision. Well known technologies, such as laser ablation, photolithography, chemical etching, electroforming and electrochemical machining, etc., can be applied during the formation of the basic molding tools for the micro lens systems.
After the molding tool is formed, polymer or copolymer materials including, but not limited to, materials such as methyl methacrylate, hydroxyethyl methacrylate, polystyrene, polycarbonate, polyolefin, styrene, silicone hydrogel, siloxane, etc. or any other suitable compositions, mixed with photo-polymerization or other suitable polymerization initiator, mold release agent and/or any other suitable additives (for anti-static, anti-scratch, . . . ), can then be dispensed in precise quantities into the molding tool. The adding of the optional dispersion materials can be done during the material mixing stage.
Soon after the micro lens materials are dispensed into the molding tool, a suitable curing process is used to cure the polymer. Depending on the choice of materials, the cured polymer can have different indexes of refraction. The steps can be repeated, manipulating the material types, material properties (surface tension and affinities) and process steps to form the various micro lens systems. The resulting micro lens systems may have different optical performance.
Once the micro lens systems are formed with the present invention, the micro lens systems and articles thereof can be used to facilitate the optical functions they are designed for. One such article uses these micro lens systems to shape the light path to improve the system performance of display devices.
The carrier media layers, which may be combinations of a reflective material, a plain transparent material, a opaque material, a metallic material, a light absorbing material, a light dispersing material or other desirable functional materials, are attached to the micro lens systems via adhesive materials or by other suitable fusing method. The functional materials can have any of the following optical properties: light dispersing, light polarizing, or anti-glare properties, or combinations of such properties.
If holes are provide in the carrier media layers, the holes may be formed with precisely controlled diameters during the formation of the carrier media layers, or via a mechanical punch or laser zapping. Along the surface of the carrier media layers there can also be alignment marks (holes) made at precisely controlled positions to facilitate alignment with the micro lens systems. Once the carrier media layers are prepared according to the desired process, suitable adhesive materials can also be pre-coated onto the carrier media layers.